1. Field of the Invention
The present invention relates to a camera apparatus for recording a photographed still picture to a record medium and a recording method thereof.
2. Description of the Related Art
Digital cameras that record digital picture information to record mediums such as a floppy disk and a semiconductor memory are becoming common. A digital camera converts a photographed picture into a digital picture signal, compresses the digital picture signal, and records the compressed picture information to a record medium. A digital camera can also record a moving picture as well as a still picture.
JPEG (Joint Photographic Experts Group) format that is a format for compressing a still picture and MPEG (Moving Picture Experts Group) format are general-purpose encoding formats adopted by ISO. These formats are suitable for picture data photographed by a digital camera and used in a personal computer. In the JPEG format, a color still picture is compression-encoded by DCT (Discrete Cosine Transform) method. Coefficient data is quantized. The quantized output is encoded with variable length code. In contrast, in the MPEG format, a color moving picture is compression-encoded. In other words, a frame difference between an input picture and a motion-compensated predictive picture is compression-encoded by DCT method. When a digital camera can record a still picture and an audio signal corresponding thereto, a memo of a still picture can be recorded as an audio signal. However, since the JPEG format is designed to record and transmit information of still pictures, audio information corresponding to still pictures cannot be simultaneously recorded and transmitted. Likewise, in other still picture formats (GIF, TIFF, BMP, and so forth), a still picture and audio information corresponding thereto cannot be simultaneously recorded and transmitted. Although software that allows a still picture and audio information corresponding thereto to be simultaneously recorded and transmitted is known (for example, Exif V.20), it is not common. Even if audio attached still picture data is created in the format of such software, software for a player that reproduces the audio attached still picture data is not easily available.
In the MPEG format, there are three types of pictures that are an I picture (Intra-coded picture), a P picture (Predictive-coded picture), and a B picture (Bidirectionally predictive-coded picture).
In the MPEG format, when a P picture or a B picture is processed, since these pictures use an inter-frame motion compensation predictive process, the circuit scale of an encoder/decoder becomes large and the number of a software process steps remarkably increases. Thus, such a process is not suitable for a small, light, and inexpensive recording/reproducing apparatus such as a digital camera. To solve such a problem, it is necessary to generate an MPEG stream composed of only I pictures. However, MPEG1 (ISO-1172-2) standard defines that the minimum frame rate is 23.97 MHz. Thus, it is difficult to form a stream composed of only I pictures without P pictures or B pictures due to the restriction of the frame rate.
Therefore, an object of the present invention is to provide a camera apparatus and a recording method thereof corresponding to the MPEG format without increasing the circuit scale and the number of process steps.
Another object of the present invention is to provide a camera apparatus and a recording method thereof that encode a still picture and audio information corresponding thereto in MPEG format that is a general-purpose format.
Another object of the present invention is to provide a camera apparatus and a recording method thereof that allow the structure of an encoder/decoder that encode a moving picture signal in the MPEG format and a still picture signal in the JPEG format to be simplified.
Another object of the present invention is to provide a camera apparatus and a recording method thereof that simultaneously record a photographed still picture and audio information corresponding thereto.
To accomplish the above-described objects, a first aspect of the present invention is a camera apparatus for encoding a video signal received from a photographing means in MPEG video format or equivalent format, encoding an audio signal received from an audio inputting means in MPEG audio format or equivalent format, multiplexing the encoded MPEG video signal and the encoded MPEG audio signal, storing the multiplexed data to a memory means, the camera apparatus comprising an I picture generating means for encoding the video signal received from the photographing means corresponding to an intra-frame encoding process so as to generate an I picture in the MPEG video format or equivalent format, and a controlling means for controlling a storing process of the multiplexed data to the memory means, wherein said controlling means generates a P picture or a B picture in the MPEG video format or equivalent format in such a manner that moving vectors of all macro blocks thereof are 0 and the chronologically preceding picture is copied as an encoded picture, wherein said controlling means encodes the audio signal received from the audio inputting means in the MPEG audio format or equivalent format so as to generate MPEG audio data, and wherein said controlling means multiplexes the I picture, the P picture or the B picture, and the MPEG audio data so as to generate the multiplexed data.
A second aspect of the present invention is a camera apparatus for encoding a video signal received from a photographing means and an audio signal received from an audio inputting means and storing the encoded signals to a memory means, the camera apparatus comprising a video encoding means for encoding the video signal received from the photographing means corresponding to a first encoding method or a second encoding method and generating first encoded video data or second encoded video data, respectively, a controlling means for controlling a storing process of data to the memory means and selecting the first encoding method or the second encoding method corresponding to a selected record mode, wherein said controlling means controls said video encoding means so as to encode the video signal corresponding to the first encoding method when a mode for recording only video data has been selected in the camera apparatus, and wherein said controlling means controls said video encoding means so as to encode the video signal corresponding to the second encoding means when a mode for recording both video data and audio data has been selected in the camera apparatus.
A third aspect of the present invention is a recording method for a camera apparatus for encoding a video signal received from a photographing means in MPEG video format or equivalent format, encoding an audio signal received from an audio inputting means in MPEG audio format or equivalent format, multiplexing the encoded MPEG video signal and the encoded MPEG audio signal, storing the multiplexed data to a memory means, the recording method comprising the steps of encoding the video signal received from the photographing means corresponding to an intra-frame encoding process so as to generate an I picture in the MPEG video format or equivalent format, generating a P picture or a B picture in the MPEG video format or equivalent format in such a manner that moving vectors of all macro blocks thereof are 0 and the chronologically preceding picture is copied as an encoded picture, encoding the audio signal received from the audio inputting means in the MPEG audio format or equivalent format so as to generate MPEG audio data, multiplexing the I picture, the P picture or the B picture, and the MPEG audio data so as to generate the multiplexed data, and storing the multiplexed data to the memory means.
A fourth aspect of the present invention is a recording method for a camera apparatus for encoding a video signal received from a photographing means and an audio signal received from an audio inputting means and storing the encoded signals to a memory means, the recording method comprising the steps of encoding the video signal received from the photographing means corresponding to a first encoding method and storing the encoded video data to the memory means when a mode for recording only video data has been selected in the camera apparatus, and encoding the video signal received from the photographing means corresponding to a second encoding method and storing the encoded video data to the memory means along with the encoded audio data when a mode for recording both video data and audio data has been selected in the camera apparatus.
According to the first aspect and the third aspect of the present invention, since the motion compensation inter-frame predictive process is not performed, the hardware scale and the number of process steps of software can be remarkably decreased. In addition, since encoded output data in the MPEG format or equivalent format can be obtained, the encoded output data can be easily used by a personal computer. With a small scale of hardware or a small number of process steps of software, as functions of a digital still camera, a moving picture recording function can be provided along with a still picture recording function. In addition, since the amount of code that is generated is small, a photographed moving picture can be recorded to an external storing medium.
According to the second aspect and the fourth aspect of the present invention, a function for simultaneously recording a still picture and an audio signal can be accomplished for a digital camera. In addition, when an audio attached still picture is recorded, only a still picture can be recorded. Thus, corresponding to a desired application, recorded data can be used.